Technical Field
The invention relates to a brine tolerant polymer composition and a process for producing and using the same and more particularly to a polymer composition used as a viscosifying agent, which is relatively insensitive to saline connate water in a subterranean oil-bearing formation.
Description of Related Art
Polymers are commonly used in oil recovery applications as viscosifying agents for fluids injected into subterranean oil-bearing formations. Applications for fluids having polymer enhanced viscosity include oil displacement in water flooding, mobility control in surfactant flooding, and permeability reduction of thief zones.
One method of increasing the viscosity of a fluid is to add extremely high molecular weight polymers to the fluid. A problem concomitant to the use of high molecular weight polymers is that the polymers often filter out the injected fluid onto the wellbore face or in the matrix pores, causing undesirable face plugging and permeability reduction. An additional problem is that high molecular weight polymers are less brine tolerant than lower molecular weight polymers, i.e., high molecular weight polymers ball up in brine, diminishing the viscosity of the polymer-containing fluid.
The art recognizes brine tolerant polymers for oil recovery applications. For example, U.S. Pat. No. 3,880,764 to Donham describes a drilling fluid composition containing a polymer and additives which render the polymer relatively brine tolerant. However, an unfilled need exists for other brine tolerant compositions useful in oil displacement flooding and other above-described applications.